1. Field of the Invention
The present invention relates to a radio telecommunication system and method, and in particular to a radio telecommunication system and method in which power consumption in mobile stations is reduced and blocking is minimized by intermittently receiving paging signals transmitted from a cell site by using a common control channel.
2. DESCRIPTION OF THE RELATED ART
A conventional battery-saving receiving processing in a mobile station is schematically shown in FIG. 7. As indicated by 401 and 402, receiving power is turned on/off periodically and repetitively in the mobile station in order to reduce power consumption. Battery saving is performed when the mobile station is waiting for a paging signal or a broadcast signal (event). When receiving power is on, the mobile station checks whether a signal is being transmitted from the cell site or not.
In response to a request from a calling subscriber, the cell site sends a plurality of paging signals to the mobile station. Upon receiving one of the plural paging signals, the mobile station stops the battery saving and turns on receiving power (404) to come into paging connection.
The above-described battery saving can be represented in a simple state transition diagram as shown in FIG. 8. Upon receiving a paging signal in a battery saving state 501, transition to a talking state (stoppage of battery saving) 502 is made in the mobile station after processing of paging connection. Further, by clearing processing, the mobile station returns from 502 to the original battery saving state 501. The mobile station thus waits for a signal fed from the cell site in waiting state.
A conventional means based upon the above described battery saving is known. In this means, the intermittence period mode is changed by using an internal watch (timer) of the cell cite in order to reduce the power consumption and weight of the mobile station. This approach will now be described by referring to FIG. 9.
First of all, the mobile station recognizes the intermittence period mode registered in the internal memory and performs initialization to set the battery saving mode at step 601. If this is performed at power-on timing, the mobile station performs initialization with a period mode produced when power is turned off.
On the basis of a timer and a flag set by itself, the mobile station itself determines whether the timing is one of intermittent-on or one of intermittent-off at step 602. On the basis of this determination, the mobile station turns off the receiving power for the intermittent-off timing and turns on the receiving power for the intermittent-on timing. Processing at step 602 corresponds to the above described battery saving operation of the mobile station.
At the time of intermittent-on (receiving power on), the mobile station checks at step 603 whether a signal (paging /broadcast) has been transmitted from the cell site. If there is not a signal from the cell site, transition to the step 602 is made. If a signal has been received, transition to paging connection processing /broadcast processing is made.
In case of broadcast processing, the mobile station forms a judgment upon information contained in the broadcast signal. If the mobile station recognizes a difference from the current period mode at step 604, the mobile station registers a new intermittence period mode at step 605 and a transition to the step 601 is made. In case of paging processing, paging connection is immediately made and a transition to the step 601 is made upon clearing.
Herein, "broadcast signal" means a signal for periodically transmitting information needed in a mobile telecommunication system (such as intermittence period mode) from a cell site.
Thus there is a scheme in which the cell site has a watch and changes the intermittence period mode systematically by using a broadcast signal at appointed times. In this scheme, the period of intermittence is prolonged to lengthen the duration of receiving power off state at night during which the frequency of use of the mobile station is low whereas the period of intermittence is shortened to shorten the duration of receiving power off in the daytime during which the frequency of use is high. Thereby, both reduction of blocking and reduction of power consumption in the mobile station are achieved with a favorable balance. Intervals of receiving power on /off of the mobile station are constant as described before.